Originally Posted by BIslander
The rears get downmixed into the surrounds in a system configured as 5.1. You don't lose anything.
Actually, it might be a little more correct to say that the 5.1 'downmix' contains as much of the 7.1 version as the mixer/author decided. In this [slightly dated] DTS-HDMA downmix panel (exemplar), you can see (in the upper half) that in downmixing from 7.1_Standard
, the content in the L+R Rear Surrounds channels is just added to the content of the L+R (Side) Surrounds channels, and L|C|R|LFE content is unchanged, in this case
. This seems [to me
] like it might be a reasonable 'default' for most mixdowns.
However, the lower half of the panel shows that in the 5.1_Standard
mixdown, the LFE signal is completely discarded.